There are numerous types of cranes for on-ship/deck operation such as rotary jib cranes with or without telescopic boom, rotary boom cranes and knuckle boom cranes.
The present invention discloses a knuckle boom crane. Traditional knuckle boom cranes consist of a pedestal for interface with the deck, slewing bearings which provides rotation to a tower, the tower is engaged with a first main boom which is pivotally hinged to the tower, whilst the other end of the main boom is pivotally connected to the knuckle boom (FIG. 1). At its extreme other end the knuckle boom is provided with one or more sheaves. Adjacent to the top of the tower and the pivot hinge of the main boom a winch is provided and optionally an operators cabin. Wire is fed from the winch via several sheaves to the sheave arranged at the extreme end of the knuckle boom and at its end the wire will typically be provided with a hook. Rotation of the winch will feed or hoist the hook at the end of the wire. The knuckle boom may be of a fixed type or a telescopic type.
The knuckle boom design is well suited for use on ship as it provides good control of the payload as the main boom and the knuckle boom as well as the wire can be operated simultaneously. This means that the booms can be lowered so as to reduce the pendulum length of the hook and thereby reduce pendulum movements of the payload.
Knuckle boom cranes suffers from some drawbacks the wire will have to travel over a numbers of sheaves which makes threading of the wire difficult, it means that there are several service points on the top of the booms which are not easily accessed as shown in a crane of the prior art in FIG. 1.
Knuckle boom cranes are usually hydraulic driven cranes, and the interface between the ship and the crane includes several hydraulic high pressure hoses in addition to this if the crane includes an operators cabin the interface will include electric power for feeding the control system in the operators' cabin.
It shall also be mentioned that heave compensation is important for on-ship operation, and that knuckle boom cranes are particularly suited for heave compensation.
It is an object according to the present invention to provide a knuckle boom crane that does not suffer from the disadvantages above, where the crane shall be adapted for applications such as:                a. Lifts from internal deck to seabed (Subsea lift)        b. Lifts between vessel and quay side in sheltered waters (Harbour lift)        c. Lifts on vessels deck (internal lift)        d. Ship to ship        